Reciprocating pump

ABSTRACT

A reciprocating pump wherein the piston rod protrudes from the cylinder for connection with a reciprocating power source; the piston rod being confined within a readily replaceable sleeve which is sealed to the piston rod and bears against the stationary seal of the pump housing in a sliding engagement. The piston rod is also stepped at the exterior of the seal to prevent the crawling of liquid leaked from the cylinder into the power source.

United States Patent 1191 I 1111 3,9

Bruggeman Nov. 18, 1975 15 RECIPROCATING PUMP 3,171,334 3/1965 Rasmussen92/165 wm 11212;: 111221 2:11:21; ...;;;;z/:2s Lake, 3,652,188 3/1972Uchiyama... 417/511 3,809,508 5/1974 Uchiyama... 417/511 I[73] Assignee:Cat Pumps Corporation,

Minneapolis, Minn. 7 Primary ExaminerWilliam L. Freeh [22] Flled' 1973Attorney, Agent, or FirmH. Dale Palmatier 21 Appl. No.1 346,726

57 ABSTRACT A reciprocating pump wherein the od p :o v [58] Field 61Search 417/510, 511, 513; nudes fmm the for a ramp rocating powersource; the piston rod being confined within a readily replaceablesleeve which is sealed to Y the piston rod and bears against thestationary seal of {[56] 1 References Cited I the pump housing in asliding engagement. The piston 1 UNITED STATES PATENTS rod is alsostepped at the exterior of the seal to pre- 1,636,614 7/1927 Prellwitz.Q 92/166 vent the crawling of liquid leaked from the cylinder 2,413,34712/1946 Hamilton et al 92/258 into the power source. 2,766,701 lO/l956Giraudeau 92/168 3,049,082 8/1962 Barry 92/86.5 12 Claims, 9 DrawingFigures j 1 5 Z Z2 v RECIPROC ATING PUMP BAcKoR'ouNDoF THE INVENTIONalong the seal which confines the pressure in the cylinl der of thepump. Furthermore, there has been a contin-.

ual crawling of liquid from the pump cylinder along the piston rod andthe liquid gets into the power side of the pump and penetrates thecrankcase and causes corrosion of the parts and other various troubles.I

SUMMARY OF THE INVENTION The reciprocating pump of the present inventionhas a piston rod connected to a reciprocating source of power to bedriven thereby. Within the pump'housing is a piston on the rod andmoving along the cylinder for accomplishing the pumping action. Areplaceable sleeve is fitted onto the piston rod, and the seal-at theend of the pump chamber bears against the seal in a sliding engagementto confine the liquid within the pump cylinder. The piston rod has astep formed at the exterior of the cylinder and the seal and to minimizemigration of liquid from the pump chamber along the rod to the powersource.

BRIEF DESCRIPTION OF THE DRAWINGS of a pump em- DETAILED DESCRIPTION OFTHE INVENTION With particular reference to FIG. 1, the pump casing orhousing 1 includes a liquid inlet manifold 2, a sleeveshaped cylinder 3,and an outlet manifold 4 from which the high pressure .liquid isdischarged. A crank rod 5 is confined within the housing 1 and is drivenby a suitable source of power so as to produce areciprocating motion ofthe end of the crank rod 5 as shown. The

crank rod 5 is connected to'a sliding crosshead 6 which slides along theguiding portion of the pump housing 1 and is rigidly connected to thepiston rod 7. The piston rod 7 has a portion of small diameterwhichextends through the inlet manifold 2 and into the cylinder 3 and aportion of somewhat larger diameter disposed between the reduceddiameter portion of the piston rod and the crosshead 6.

The piston rod 7 serves to reciprocate a resilient rubber piston cup 8which is carried on a piston valve body 10 concentric of the piston rod7, but defining an annular flow passage or space 9. The piston body 10is movable longitudinally relative to the piston rod 7, but is confinedfor limited longitudinal movement by a valve disc or element 11 affixedto the piston rod 7, and an apertured disc 12 through which liquid mayflow. The end of piston body 10 will seal against the valve element 1]when the piston rod 7 is thrust forwardly toward the outlet manifold 4.The resilient piston cup 8 seals against the interior of the cylinderwall 3 in air and liquid sealing relation.

An outlet check valve is defined by movable valve element l6 pressed byspring 14 against a valve seat 15 so that liquid is allowed to flow fromthe cylinder 3 through the outlet manifold 4, but reverse flow of liquidis prevented.

Upon reciprocation of piston rod 7, the forward stroke of the rod causesthe valve element 11 to seal against the valve body 10 as shown andforce the liquid forwardly through the outlet manifold 4. Upon reversalof the piston rod, the valve element 11 is drawn away from the pistonbody 10 to permit liquid to flow through the passage 9 as the apertureddisc 12 bears against the end of piston body 10 and produces thecorresponding reverse movement of the valve body and piston cup alongthe cylinder 3. In the form shown, the rod 7 has only a short length ofstroke, and less than half the length of the cylinder 3 is utilized.

According to the present invention, the outside of piston rod 7 isenclosed within a sleeve 19 which is sealed to the rod by sealing ringsor O-rings 17, 18. A sealing element 20 is stationary with the housingor casing 1 and seals against the exterior of sleeve 19 for shutting offor isolating the inside of the cylinder 3 from the drive source adjacentcrosshead 6. The sealing element 20 will slide over the sleeve 19whereby any abrasion that occurs will cause a wearing of the readilyreplaceable sleeve 19 and will have no wearing effect upon the pistonrod 7. Renewal only requires the replacement of the sleeve 19.

In the piston rod 7 itself, its diameter is reduced at a step 21. Inmost cases, the piston rod 7 will have a smaller diameter within thecylinder 3 and a larger diameter at the exterior of seal 20, asillustrated. The step 21 in the piston rod effectively prevents crawlingor migration of the liquid from cylinder 3 along the rod 7, even if someof this liquid gets by the seal 20. The pump illustrates a secondsealing element 22 in the housing or casing and in sealing engagementwith the large diameter portion of the piston rod 7. The sealing element22 bears against the piston rod with only a relatively light pressure sothat the friction is relatively slight. Accordingly, the sealing element22 may contact the piston rod 7 directly and without interposing a wearsleeve therebetween.

It should be noted that the sleeve 19 bears tightly against both thevalve element 11 and the step 21 in piston rod 7, and the sleeve istightly sealed to the piston rod by the O-rings. The tendency of liquidto migrate along the piston rod effectively causes the liquid tomigrate-along the exterior of sleeve 19 and therefore the step 21 iseffectively between the sleeve 19 and the enlarged diameter portion ofpiston rod 7 adjacent the seal 22.

In the form of the invention illustrated in FIG. 2, the pump is verysimilar to that illustrataed in FIG. 1, and, accordingly, the samereference numerals are used in FIG. 2 to depict all of the parts whichare the same in FIG. 2. The piston rod 7.2 has a uniform size throughoutthe length of it, from the valve element 11 to the crosshead 6. Theremovable sleeve 19.2 has the same length as the portion of piston rod7.2 from the valve element 11 to the crosshead 6, and the seal 20 willslidingly engage and seal against the sleeve 19.2 similar to thatpreviously described in connection with FIG. 1.

The sleeve 19.2 is sealed to the piston rod 7.2 by seal rings 17.2 and18.2 to prevent any of the liquid from cylinder 3 from flowing insidethe sleeve 19.2. The interior size of seal 22.2 is fitted to correspondwith the exterior dimensions of the sleeve 19.2

The form of the pump illustrated in FIG. 3 is substantially the same asthe pump illustrated in FIG. 1, and, accordingly, the same referencenumerals are utilized for the same parts. In the pump of FIG. 3, thepiston rod 7.3 is of uniform diameter throughout the entire length ofit. The piston rod 7.3 carries a pair of reciprocating sleeves 19.3a and19.3b which are sealed to the piston rod by sealing rings 17.3 and 18.3.It will be noted that the sleeves 19.3aand 19.3b engage and slide alongthe seals and 22.3 as the piston rod reciprocates. Any abrasion whichmay occur at the seals 20 and 22.3, will cause wearing of the sleevesinstead of the piston rod and the sleeves may be readily and easilyreplaced.

The FIGS. 4-9 illustrate various forms of the pump incorporating thepresent invention, and FIG. 4 illustrates the identical form of pumpfully illustrated in FIG. 1 wherein the piston rod 7 has a step 21intermedi- I ate the ends of it at which place the piston rod changesits diameter, and the piston rod is provided with a sleeve 19 which isengaged by the seal 20. In all of the other diagrammatic views, FIGS.59, the pumps are substantially the same as illustrated in FIG. 1 inmost respects, and the same reference numerals are utilized for similarparts.

In FIG. 5, a sleeve 19.5 is also mounted on and sealed to the portion ofpiston rod 7 of enlarged diameter. Sealing between the sleeve 19.5 andpiston rod 7 is accomplished by the sealing rings 18.5. The seal 22.5 isadjusted to correspond to the size of the outside of sleeve 19.5.

In the form illustrated in FIG. 6, the piston rod 7 has the same step 21intermediate the ends of it, but the encompassing sleeve, found in FIG.1, is eliminated from this form of pump illustrated in FIG. 6.Accordingly, the seal 20.6 is adjusted in size so as to bear against andseal with the piston rod 7 as the rod reciprocates during pumping.

In the form illustrated in FIG. 7, the replaceable sleeves have beeneliminated,-and, in this form, the piston rod 7.7 hasits end of enlargeddiameter extending into the cylinder 3 and through the seal 20.7. Thereduced diameter portion of rod 7.7 is at the exterior of the seal 20.7,and the step 21.7 is also disposed at the exterior of the seal 20.7 andadjacent the other seal In the form of the pump illustrated in FIG. 8,the piston rod 7.8 has an enlarged portion, intermediate its ends, andthe two ends of the piston rod 7.8 are of similar sizes, but reduced ascompared to the larger diameter of the intermediate section of the rod.The larger section of the piston rod 7.8 engages and is sealed againstthe seal 20.8, and the step 21.8 is again disposed intermediate the twoseals 20.8 and 22.8.

In the form of the pump illustrated in FIG. 9, the piston rod 7.9 hasportions of enlarged diameter at the locations where the piston rodpasses through the seals 20.9 and 22.9, and the remaining portions ofthe piston rod 7.9 are of reduced diameter. It will be particularlynoted that, in this form, the piston rod has two adjacent steps 21.9aand 21.9b cooperating to prevent migration by crawling of the liquidalong the piston rod.

It will be seen that this pump of the present invention incorporatesinto the piston rod, a step in the size ofthe piston rod to prevent andlimit the migration of liquid along the rod. The step in the size of thepiston rod is located at the exterior of the principal seal whichseparates the high pressure in the cylinder from the exterior. Inaddition, the present invention provides the reciprocating sleeve on theportion of the piston rod which passes through the seal so that anyabrasion or wear which occurs will occur on the readily replaceablesleeve to minimize any effect upon the piston rod.

What is claimed is:

1. A reciprocating pump to be operated by a source of mechanical power,comprising a pump cylinder having a liquid inlet and outlet, a pistonrod to be driven by the source of power and extending into the cylinder,a piston on the end of said piston rod and confined within the cylinderfor sliding movement within a predetermined length of stroke, a sleevereplaceably mounted concentrically on the piston rod for movementtherewith, a first sealing element at the end of the cylinder andengaging and sealing against a portion of the sleeve with a lengthapproximately the length of stroke, a second sealing element sealingagainst a portion of the sleeve externally of the cylinder and spacedfrom the first sealing element, the piston rod having a step changingthe diameter of the rod and positioned at the exterior of the cylinderto prevent liquid from the cylinder from creeping along the piston rodto the source of power.

2. The reciprocating pump of claim 1 in which the sleeve is radiallyspaced from the rod to define an annular opening therebetween, and 0rings in said annular space and adjacent ends of the sleeve for mountingthe sleeve to the piston rod.

3. The reciprocating pump of claim 2 wherein the piston includes apiston body moveable longitudinally relative to the piston rod, 21 valvedisc affixed to the piston rod and sealable against the piston body, andwherein said step provides a shoulder facing the piston body, the endsof the sleeve abutting the valve disc and the shoulder, respectively.

4. A reciprocating pump to be operated by a source of mechanical'power,comprising a pump cylinder having a liquid inletand outlet, a piston rodto be driven by the source of power and extending into the cylinder, apiston on the end of said piston rod and confined within the cylinderfor sliding movement within a predetermined length of stroke, a sleevemounted to and carried concentrically of the piston rod and spacedradially outwardly therefrom, a first sealing element at the end of thecylinder and engaging and sealing against a portion of the sleeve with alength approximating the length of the stroke, and a second sealingelement sealing against a portion of the piston rod externally of thecylinder and spaced from the first sealing element, the piston rodhaving a step changing the diameter of the rod and positioned at theexterior of the cylinder between the first and second sealing elementsto prevent liquid from the cylinder from creeping along the piston rodto the source of power.

5. A reciprocating pump as defined in claim 4 in which the rod has alarge diameter portion within the cylinder and a relatively smallerdiameter portion adjacent the step and spaced along the rod from theseal at the exterior of the cylinder.

6. The reciprocating pump according to claim 4 in which the piston rodhas a relatively small diameter portion within the cylinder andextending through the first sealing element, said piston rod having arelatively larger diameter portion adjacent the step and spaced alongthe rod from the seal at the exterior of the cylinder.

7. A reciprocating pump to be operated by a source of mechanical power,comprising a pump cylinder with a fluid inlet and outlet, a piston rodto be driven by the source of power and extending into the cylinder, apiston at the end of the piston rod and confined within the cylinder forsliding movement with the rod, a replaceable sleeve concentric with thepiston rod and spaced radially outwardly therefrom, and 0 rings mountingthe sleeve to the piston rod and providing seals between the sleeve andpiston rod adjacent ends of the sleeve, and a sealing element at the endof the cylinder and in sealing and sliding contact with said sleeve andcooperating with the sleeve to maintain the fluid pressure differentialbetween the interior and exterior of the cylinder.

8. A reciprocating pump as defined in claim 7 in which said sleeveextends along the whole length of the piston rod.

9. The reciprocating pump according to claim 7 in which said sleeve isfitted on the piston rod as only the 6 portion thereof in slidingcontact with the sealing element.

10. The recriprocating pump according to claim 7 and also including ahousing connected to the cylinder and encompassing the piston rod, asecond sealing element within the housing and encompassing the pistonrod in spaced relation with said first mentioned sealing element, andsleeve means including said sleeve and fitted on the rod to engage andslide through both of said sealing elements as the piston rod isreciprocated.

11. The reciprocating pump of claim 7 wherein the piston includes apiston body moveable longitudinally relative to the piston rod and avalve disc affixed to the piston rod and scalable against the pistonbody, and wherein the piston rod includes a shoulder at the exterior ofthe cylinder, the ends of the sleeve abutting the valve disc and thepiston rod shoulder, respectively.

12. The reciprocating pump of claim 11 wherein the end of the piston rodwithin the cylinder is threaded, and wherein the piston body isremoveably mounted to; the piston by a nut threaded onto the threadedend of the piston rod, whereby removal of the nut permits removal of thepiston and sleeve to afford replacement of the latter.

1. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder having a liquid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston on the end of said piston rod and confined within the cylinder for sliding movement within a predetermined length of stroke, a sleeve replaceably mounted concentrically on the piston rod for movement therewith, a first sealing element at the end of the cylinder and engaging and sealing against a portion of the sleeve with a length approximately the length of stroke, a second sealing element sealing against a portion of the sleeve externally of the cylinder and spaced from the first sealing element, the piston rod having a step changing the diameter of the rod and positioned at the exterior of the cylinder to prevent liquid from the cylinder from creeping along the piston rod to the source of power.
 2. The reciprocating pump of claim 1 in which the sleeve is radially spaced from the rod to define an annular opening therebetween, and O rings in said annular space and adjacent ends of the sleeve for mounting the sleeve to the piston rod.
 3. The reciprocating pump of claim 2 wherein the piston includes a piston body moveable longitudinally relative to the piston rod, a valve disc affixed to the piston rod and sealable against the piston body, and wherein said step provides a shoulder facing the piston body, the ends of the sleeve abutting the valve disc and the shoulder, respectively.
 4. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder having a liquid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston on the end of said piston rod and confined within the cylinder for sliding movement within a predetermined length of stroke, a sleeve mounted to and carried concentrically of the piston rod and spaced radially outwardly therefrom, a first sealing element at the end of the cylinder and engaging and sealing against a portion of the sleeve with a length approximating the length of the stroke, and a second sealing element sealing against a portion of the piston rod externally of the cylinder and spaced from the first sealing element, the piston rod having a step changing the diameter of the rod and positioned at the exterior of the cylinder between the first and second sealing elements to prevent liquid from the cylinder from creeping along the piston rod to the source of power.
 5. A reciprocating pump as defined in claim 4 in which the rod has a large diameter portion within the cylinder and a relatively smaller diameter portion adjacent the step and spaced along the rod from the seal at the exterior of the cylinder.
 6. The reciprocating pump according to claim 4 in which the piston rod has a relatively small diameter portion within the cylinder and extending through the first sealing element, said piston rod having a relatively larger diameter portion adjacent the step and spaced along the rod from the seal at the exterior of the cylinder.
 7. A reciprocating pump to be operated by a source of mechanical power, comprising a pump cylinder with a fluid inlet and outlet, a piston rod to be driven by the source of power and extending into the cylinder, a piston at the end of the piston rod and confined within the cylinder for sliding movement with the rod, a replaceable sleeve concentric with the piston rod and spaced radially outwardly therefrom, and O rings mounting the sleeve to the piston rod and providing seals between the sleeve and piston rod adjacent ends of the sleeve, and a sealing element at the end of the cylinder and in sealing and sliding contact with said sleeve and cooperating with the sleeve to maintain the fluid pressure differential between the interior and exterior of the cylinder.
 8. A reciprocating pump as defined in claim 7 in which said sleeve extends along the whole length of the piston rod.
 9. The reciprocating pump according to claim 7 in which said sleeve Is fitted on the piston rod as only the portion thereof in sliding contact with the sealing element.
 10. The recriprocating pump according to claim 7 and also including a housing connected to the cylinder and encompassing the piston rod, a second sealing element within the housing and encompassing the piston rod in spaced relation with said first mentioned sealing element, and sleeve means including said sleeve and fitted on the rod to engage and slide through both of said sealing elements as the piston rod is reciprocated.
 11. The reciprocating pump of claim 7 wherein the piston includes a piston body moveable longitudinally relative to the piston rod and a valve disc affixed to the piston rod and sealable against the piston body, and wherein the piston rod includes a shoulder at the exterior of the cylinder, the ends of the sleeve abutting the valve disc and the piston rod shoulder, respectively.
 12. The reciprocating pump of claim 11 wherein the end of the piston rod within the cylinder is threaded, and wherein the piston body is removeably mounted to the piston by a nut threaded onto the threaded end of the piston rod, whereby removal of the nut permits removal of the piston and sleeve to afford replacement of the latter. 